For a century Friedel-Crafts type reactions were carried out in solution using AlCl.sub.3 and related Lewis acid halide type catalysts. These reactions, some of which gained very significant industrial application, such as the ethylation of benzene, the isobutylation of isobutylene, the isomerization of hydrocarbons, are all well recognized to involve the formation of highly colored complex layers (so called "red oils"). Decomposition of the complex layers necessitates additional steps and generally results in the loss of the catalyst.
The realization of the nature of the Friedel-Crafts reactions and their catalyst resulted in an understanding of the generalized acid catalyzed characteristics of these reactions, and allowed the use of a large variety of not only Lewis, but of Bronsted acid type catalyst systems. The use of supported solid acid catalysts, allowing catalytic heterogeneous reactions, was, until recently, of limited scope. They were utilized only in specific instances, such as in the preparation of cumene via propylation of benzene with propylene, using catalysts of the supported solid phosphoric acid type. Similar reaction conditions for the preparation of ethylbenzene from benzene and ethylene were found less satisfactory. Ethylation was observed to take place only at higher temperatures, and, even more significantly, the transethylation of benzene with di- or polyethylbenzenes inevitably formed in the reactions, is not satisfactorily realized under heterogeneous catalytic conditions.
Friedel-Crafts isomerization of hydrocarbons, such as of alkanes to highly branched isomeric mixtures or the isomerization of dialkylbenzenes, such as xylenes, was also until now predominantly carried out with liquid Friedel-Crafts catalyst systems, such as AlBr.sub.3, AlCl.sub.3, HF--BF.sub.3, and the like.
The formation of complexes with AlCl.sub.3, or related catalysts, generally necessitate the use of molar excess of "catalyst" as well as decomposition of stable catalyst-product complexes, and limit the industrial and practical use of liquid phase Friedel-Crafts reactions compared with other catalytic systems, such as metal and organometallic catalyzed transformation reactions, isomerization, and the like.
It is on this basis, consequently, that there is substantial practical significance in this invention to modify the usual Friedel-Crafts type reactions in a way, which can be described on the basic principle, to utilize high acidity supported catalysts, in which the acidity is provided by a higher perfluorinated alkanesulfonic acid (C.sub.n F.sub.2n+1 SO.sub.3 H; n=4-18) bonded to a higher valence metal fluoride, preferentially antimony pentafluoride, tantalum pentafluoride or niobium pentafluoride.
Liquid superacid catalysts, such as magic acid, FSO.sub.3 H--SbF.sub.5, fluoroantimonic acid, HF--SbF.sub.5 or CF.sub.3 SO.sub.3 H--SbF.sub.5 have estimated acidities on the logarithmic Hammett acidity scale reading up to about -25 (as compared with -11 for 100% sulfuric acid, or -10 for 100% HF) and are, thus, up to 10.sup.14 times stronger than conventional strong mineral acids.
The solution chemistry of superacids was well documented in recent years. It was based on this background that it was attempted to attach these superacid systems to suitable solid supports. Difficulties in achieving this goal are, however, significant. For example, BF.sub.3 based systems such as the HF--BF.sub.3, cannot be efficiently absorbed onto solid supports because of the great ease with which BF.sub.3 (as well as HF) is desorbed from these solid supports. AsF.sub.5, SbF.sub.5, TaF.sub.5, NbF.sub.5, having lower vapor pressures and increased ability for fluorine-bridging, are somewhat more adaptable to be attached to solid supports. Due to the extreme chemical reactivity of SbF.sub.5, and related higher valency metal fluorides, it was found that they can be attached only satisfactorily to fluorinated carriers, such as fluorinated alumina.
SbF.sub.5 --FSO.sub.3 H (magic acid) or SbF.sub.5 --CF.sub.3 SO.sub.2 H on fluorinated-alumina, at 70.degree., isomerizes straight chain alkanes such as n-heptane, or n-hexane. (U.S. Pat. No. 3,766,286) or catalyzes the alkylation of alkanes or aromatic hydrocarbons (U.S. Pat. No. 3,708,553).
Trifluoromethanesulfonic acid (CF.sub.3 SO.sub.3 H)--SbF.sub.5 supported catalyst was disclosed for the hydroisomerization of paraffins (U.S. Pat. No. 3,878,261) but the prior art does not teach or disclose the use of higher perfluorinated alkanesulfonic acids in solid superacidic catalyst compositions. This is understandable since one would expect the acidity of the higher perfluorinated alkanesulfonic acids to decrease to a significant extent. Supported SbF.sub.5 --FSO.sub.3 H or SbF.sub.5 --CF.sub.3 SO.sub.3 H catalysts are effective for isomerization and alkylation reactions, but show limited adherence of the catalyst to the surface, mostly due to the relative volatility of fluorosulfuric or trifluoromethanesulfonic acid.
SbF.sub.5, NbF.sub.5 and TaF.sub.5 based superacids can also be deposited on inert polyfluorinated polymer supports (Teflon, Kel-F and the like) or on fluorinated polycarbon (coke). Adherence to these surfaces, however, is also limited. They can also be intercalated into graphite or fluorinated graphite (as in U.S. Pat. No. 4,116,880) but these catalysts utilize only surface exposed acids and not those maintained in the graphite layers.